Group III nitrides such as GaN have superior semiconductor properties and are therefore used as materials suitable for semiconductor devices. In addition, group III nitrides such as GaN have excellent material properties different from those of Si, GaAs, SiC, or the like for different types of semiconductor devices such as light-emitting device and electronic device for example, and can therefore be used for a variety of devices.
For example, Japanese Patent Laying-Open No. 2009-126722 (PTD 1) discloses a free-standing group III nitride substrate to be used as a substrate for a semiconductor device. The free-standing group III nitride substrate has a diameter of 25 mm or more and 160 mm or less and a thickness of 100 μm or more and 1000 μm or less. It discloses, as a specific example thereof, a free-standing GaN substrate having a diameter of 100 mm and a thickness of 400 μm.
Japanese Patent Laying-Open No. 2008-010766 (PTD 2) discloses a GaN-thin-film-bonded substrate to be used as a substrate for manufacturing a semiconductor device. The GaN-thin-film-bonded substrate includes a heterogeneous substrate whose chemical composition is different from that of GaN, and a GaN thin film having a thickness of 0.1 μm or more and 100 μm or less and bonded to the heterogeneous substrate. It discloses, as a specific example thereof, a GaN-thin-film-bonded substrate having a diameter of 50.8 mm and including a sapphire substrate and a GaN thin film having a thickness of 0.1 μm or 100 μm and bonded to the sapphire substrate.
Japanese Patent Laying-Open No. 2010-182936 (PTD 3) discloses a composite substrate to be used as a substrate for a semiconductor device. The composite substrate includes a support substrate, a nitride semiconductor layer, and a joint layer disposed between the support substrate and the nitride semiconductor layer. It discloses, as a specific example thereof, a composite substrate having a diameter of 50.8 mm and including a sapphire substrate, a GaN layer, and a joint layer formed by press fitting between the substrate and the GaN layer, in which the GaN layer has a thickness of 5 μm to 220 μm.